Silicate glass and glass-silicon nitride composite coatings were atmospheric plasma sprayed onto mild carbon steel substrates under varying process parameters such as torch power and H2/Ar ratios. The x-ray analysis revealed that Si3N4 in the composite coatings could be preserved under the harsh environmental conditions of the plasma spray process. The presence of Si3N4 as the reinforcement phase to the glass matrix conferred higher hardness properties to the coatings.